Simplify to lowest terms. $\dfrac{15}{20}$
Solution: What is the greatest common factor (GCD) of 15 and 20? $15 = 3\cdot5$ $20 = 2\cdot2\cdot5$ $\mbox{GCD}(15, 20) = 5$ $\dfrac{15}{20} = \dfrac{3 \cdot 5}{ 4\cdot 5}$ $\hphantom{\dfrac{15}{20}} = \dfrac{3}{4} \cdot \dfrac{5}{5}$ $\hphantom{\dfrac{15}{20}} = \dfrac{3}{4} \cdot 1$ $\hphantom{\dfrac{15}{20}} = \dfrac{3}{4}$